1. Field of the Invention
The present invention relates to a charging apparatus and a charging method, and more specifically to a novel, next-generation charging apparatus and charging method for secondary cells requiring charging.
2. Description of the Related Art
In recent years, there has arisen an urgent need for the development of a charging apparatus or charging method for efficiently executing charging processing of a secondary cell.
More specifically, while at present a huge number of secondary cells are used in a wide range of fields, because there is no simple, efficient charging apparatus or method available, secondary cells which can still be charged are treated as if they are secondary cells that cannot be charged, there being an increasingly large number of such secondary unutilized secondary cells to be found in homes, resulting in not only worsening environmental problems, but also a great amount of waste and increase in cost.
In the past, equipment manufacturers made products that could not be used unless the secondary cells therein were charged by a charger, designing equipment that encompassed the characteristics of the secondary cell to be used, thereby forcing consumers to purchase a charger as part of the product.
For this reason, consumers themselves unconsciously came to think of the charger as being part of the product, so that even if better batteries or chargers were to be available on the market, there was absolutely no effort made to correct the mistaken impression of consumers that these would be an added expenses, and that only the batteries and charger provided by the manufacturer could be considered proper components that could enable them to avail themselves of the maximum performance, so that in the extreme cases batteries and chargers were considered inviolable holy cows, with all second-source batteries and chargers considered inferior by comparison, these concepts controlling the minds of consumers.
The only exception to the above-noted situation is that which occurs when a single primary cell of a toy, a flashlight or a TV terminal or the like becomes depleted, in which case the users gets by with another battery purchased at a supermarket or appliance store.
The most common typical example of the current situation is that of cellular telephones, the reason for this being that sealed battery covers of the slide-in type are common in the field of secondary cells, the secondary cell being housed therewithin. It is not even possible for the consumer to open the sealed secondary cell cover, and even if a second source battery maker were to manufacture a good secondary cell, it would be nearly impossible to accommodate hundreds of different types of cellular telephone covers, not to mention the fact that cellular telephone manufacturers continue to introduce new models to the market every three months, making it impossible to keep up with manufacturing of secondary cell covers to accommodate the constantly appearing new models of cellular telephones.
Large-capacity electrical tools also fall into this category.
Given the above-described situation, nickel-hydrogen secondary cells that should be able to tolerate more 1000 charges and nicad batteries that should be able to tolerate over 1500 charges are no longer able to hold their capacity after just 200 or 300 charges, thereby forcing consumers to replace relatively high-cost pack batteries prematurely.
The main reason for this is that the a charging method developed more than 40 years ago, this being the negative delta V method, in which overcharging, which is the most severe treatment of secondary cells, inevitably occurs is used in the chargers provided by all manufacturers. The resulting overcharging causes a breakdown of the chemical function with in the secondary cell, so that at 200 to 300 charges the consumer is forced to spend a high amount of money to replace the secondary cell.
In a negative delta V charging system of the past, nicad and particularly nickel-hydrogen charging requires as long a time as 2 hour and 30 minutes, and even after this charging discharging tests on nickel-hydrogen batteries of typical Japanese manufacturers reveals no more than 60% or 75% charge ratio, and it is not possible to expect 100% charge ratio.
In particular in the case in which there is, for example, 25% of capacity remaining in a battery, the ideal method for increasing the charging ratio is to achieve a 100% discharge, so as to bring the battery to the 0% charge level, and then perform charging. Unless this is done, it is almost impossible with negative delta V charging to raise the charge of the battery from the residual charge of 25%, that is to raise the charge level from 26% to 100%. This being the case, if the discharging time is 1 hour, a charging time of 3 hours is necessary, this representing a considerable disadvantage to a user wishing to quickly charge the battery.
The above situation is caused by the “memory effect,” which is a characteristic of nicad and nickel-hydrogen batteries.
In the case of an electric drill, of course, unless the battery can be charged completely in approximately 10 minutes, it would be necessary for an electrical worker to carry five or six electric drills with fully charged batteries. Recently, however, if slight battery damage is allowed, rechargeable electric drills with a charging rate of 6 C (10 minutes) have become available. These products, however, make a high-cost switching regulator type power supply in order to source a high current at one time an essential part, so that such electric drills that can be charged in 10 minutes must be priced at approximately 40,000 yen or higher for retail sale.
Because of overheating of the secondary cells that are used, replacement is necessary after approximately 100 charges.
What is most required when performing charging is a charging method that is suited to the characteristics of the battery or battery pack at the time of charging.
This is easy to express in words, but in reality (1) the characteristics and internal resistances of batteries of various battery manufacturers are mutually different, (2) there are differences in charging characteristics of batteries of even the same manufacturer, (3) if a battery or battery pack is left unused for a long period of time, in the case of an absolutely new battery there are a great many cases in which the battery is almost entirely unactivated (unformed), and such batteries must be activated when being charged, and (4) in particular in the case of a battery pack formed by 4 or 6 single cells connected in series, if just one of the cells is unformed or faulty, it is almost impossible to achieve the desired battery capacity.
A charging method for a secondary cell that reliably solves the numerous above-noted problems is a pre-requisite as a next-generation secondary cell charging method.
The present invention is directed not only at educating consumers with regard to the various above-described problems, but also at removing the above-noted problems by operating a PC, a device which is highly accessible to today's consumers, thereby providing an ideal method of charging, thereby providing consumers with a significant social advance.
Accordingly, it is an object of the present invention, to improve on the above-noted drawbacks in the prior art, to provide a charging apparatus and a charging method capable of reliably achieving full charging of a prescribed secondary cell in a short period of time and using a simple apparatus. It is a further object of the present invention to provide a charging apparatus and charging method which, by extending the life of a secondary cell, can solve both environmental and resource problems, and which can execute charging processing of a secondary cell, making easy use of a home-use PC(PC) in an interactive manner.